ROCOM

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ROCOM ( RO ssendorf CO olant M ixing Model) was a test facility for investigating the coolant mixing within a nuclear reactor .

It was built in 1998 at the Institute for Security Research at the Helmholtz Center Dresden-Rossendorf . The system reproduced the primary circuit of a German pressurized water reactor of the Konvoi type on a scale of 1: 5 . ROCOM had replicas of all four cooling loops, each equipped with an individually controllable circulation pump, it was operated with water under ambient conditions.

The background to the experiments was the investigation of the mixing of water with different boron concentrations: In the type of reactor examined, boron was added to the water used as a coolant in order to control the chain reaction within the fuel. Boron is a very effective neutron absorber that catches excess neutrons.

As part of safety considerations, accident scenarios were examined in which the boron concentration in parts of the reactor plant did not correspond to the specified value. It is conceivable, for. B. the feeding of water with too low a boron concentration. To assess the safety of the reactor, it is important to know how this underborated water mixes with the normally borated water in the system. The experiments at ROCOM were carried out precisely on this question. Differences in the boron concentration were simulated using a salt solution that influenced the electrical conductivity. Saline and non-saline water mixed in the pilot plant in the same way as water with and without boron in the original reactor.

With the aid of so-called grid sensors, the distribution of the salt concentration was measured at points of interest in the test facility. The grid sensors consist of two levels of wire grids, which are spanned a short distance from each other in the flow cross-section. An electrical voltage is applied to one wire level and the current flowing away is measured on the second wire level. The corresponding salt concentration can be determined from the value of the measured current flow. These data are then converted into boron concentration values, which are then used in the corresponding safety analyzes.

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